Thermostatic control



APFIIH 9 W359 w. J. MCGOLDRICK 1,997,262

THERMOSTAT I C CONTROL Filed Dec. 1, 1933 2 Sheets-Sheet l April 9, 1935. w. J. MCGOLDRICK 1,997,262

THERMOS TATI C CONTROL Filed Dec. 1, 1935 2 Sheets-Sheet 2 FIG. 5.

Patented Apr. 9, 1935 UNITED STATES PATENT OFFICE THERMOSTATIC CONTROL Application December 1, 1933, Serial No. 700,411

7 Claims.

This invention relates to thermostatic controls, and with regard to certain more specific features, to thermostatic electric switches.

Among the several objects of the invention may be noted the provision of a thermostatic electric switch of the class described which is compact in structure and which is adapted to be applied, as

a unit, to any surface the temperature of which it is desired to control; a thermostatic switch of the class described including means operating to conduct heat efiiciently from the surface the temperature of which is to be controlled, to the thermostatic actuating element thereof; a switch of the class described including means for accurately adjusting the temperature at which the switch operates; a switch of the class described including improved means for transmitting the motion of the thermostatic element to the electrical contacting means; and the provision of a thermostatic electric switch of the class described which is relatively simple in construction and operation. Other objects will be in part obvious and in part pointed out hereinafter;

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which is illustrated one of various possible embodiments of the invention.

Fig. 1 is a front elevation of a thermostatic electric switch embodying the present invention,

-5 as applied to a pipe in order to be responsive to the temperature thereof;

Fig. 2 is a front elevation of the switch of Fig. 1, but with a cover portion removed;

Fig. 3 is a vertical cross-section of the switch of Figures 1 and 2, taken substantially along lines 3-3 of Fig. 1;

Fig. 4 is a top plan view of the switch shown in Fig. 2;

Fig. 5 is a horizontal cross-section taken substantially on lines 5-5 of Fig. 3; and

Fig. 6 is a cross-section taken substantially along lines 6-5 of Fig. 3.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now more particularly to Fig. 1, numeral 5 indicates a pipe, which, under normal circumstances, may be considered as conducting a fluid, the temperature of which it is desired to control. For example, the pipe i may comprise a hot water outlet, or riser, of a household hot water heating plant. Inasmuch as the pipe I is usually made of such material as is a good heat conductor, it will be apparent that the temperature of the surface of the pipe I will substantially correspond to the temperature of the fluid moving in the pipe I. The present invention comprises a. switch which is attached to the pipe I, or any similar element, in order to be responsive to the temperature of the surface thereof, and to motivate electrical contact or switch means whereby the heat generating apparatus (for example, the oil burner) is controlled with respect to that temperature.

Numeral 3 indicates broadly the switch of the present invention. It is attached to the pipe I, for example, by means of straps 5. An electrical cord or cable I entering the switch 3 provides for electrical connections to said switch.

Referring also to Fig. 2, numeral 9 indicates a rectangular frame, which forms the supporting base for the various elements going to make up the switch 3. From the frame 9, at right angles to the plane thereof, extends a pair of cars or brackets II, which receive machine screws 13. The screws l3 serve to hold in position, on the frame 9, a casing or cover member l5. The cover l5 suitably comprises molded phenolic or like insulating material.

Also extending from the frame 9, at the top thereof, is a bracket Il, while at the bottom of the frame 9 a similar bracket I9 is provided. The bracket ll supports temperature adjusting means later to be described, while the bracket l9 supports an electrical contact plate 21, also to be described hereinafter. Also extending from the frame 9, on the outer edge thereof, is a bracket 22, which receives an insulating ring 23. The ring 23 is held in position on the bracket 22 by a wire snap ring 25. Through the central opening 21 of the ring 23 passes the conduit or cord '3.

Numeral 29 indicates an upper heat conducting, thermostatic actuator mounting element, which is preferably made of aluminum or some other metal of high heat conductivity and low heat capacity. The element 29 comprises a circular horizontal portion ill and a relatively flat vertical portion 33. The outer face of the portion 33 is curved to fit tightly against the pipe l, or other device upon which the switch is to be mounted, as is shown at numeral 35 in Figures 3 and 4.

Mounted in juxtaposition to the element 29 is another element 3i of similar shape and function. The element 3! also has a circular horizontal portion 99 and a vertical portion 9!, the portion 9! likewise being provided with a curved surface 93 for engaging the surface of the pipe I. The portions 35 and 93 of the respective members 29 and 31 in effect form a continuation of each other, as is apparent from Fig. 3. The

central portions 38 and 39 are inwardly hollow,

having conical recesses 99 and 91 respectively. Recesses 95 and 97 provide a central chamber 99 which receives a thermostatic actuating element 5! to be described hereinafter.

Screws 53 (Figures 2 and 3) hold the portions 3| and 99 together as a unit, while screws 55 hold the members 29 and 31, as an assembly, to the frame 9, spaced therefrom by heat insulating spacer blocks 57. The screws 55 also serve to support, by clamping between the blocks 5? and the frame 9, a back cover plate 59. The plate 59 is preferably formed from insulating material and has a central opening 6i therein to accommodate the circular portions 9i and 39 of the elements 29 and 31, respectively. This arrangement provides spaces 93 (Fig. 3) between the elements 29 and 37, and the plate 99, through which spaces 93 the bands 5 (Fig. 1) are passed in order to secure the switch to the pipe or the like.

In the chamber 99, there is loosely clamped, by means of the portions 3! and 39, the thermostatic actuating element 5!, which comprises a composite thermostatic metal disc having radial corrugations 65 therein (see Fig. 5), but having a flat periphery 67, and a central opening 69, this actuating element being of the type shovm in John A. Spencer Patent No. 1,895,591. No detailed description of this actuating element will be given herein, reference being directed to said patent therefor. However, it may be said that it comprises a bimetallic or like device which is essentially slightly conical in one direction, but which, under conditions of temperature change of a predetermined magnitude, reverses its direction of conicity with a snap action. The reversal of direction of conicity causes the central portion of the disc 5i surrounding opening 69 to move through an appreciable amplitude, and it is this motion which is used for achieving a switch control in the present invention.

The actuator 5|, as has been indicated, is secured in position by loosely clamping its flat peripheral rim 67 between the two portions 3! and 39 of the elements 29 and 31.

As the elements 29 and 31 are both formed of good heat conducting material of low heat ca pacity, it will readily be seen that the actuator 5|, through direct contact therewith, and by radiation and convection between it and the enclosing walls, is maintained at all times at substantially the temperature of the surface of the pipe i. The manner in which the actuator 5i is shielded by its enclosure from radiation and conduction to and from objects other than the elements 29 and 91, and from external air currents, is also believed to be an important factor contributing to the unusually close correspondence of the temperature of the actuator 98 and the temperature of the surface of pipe 5.

As is disclosed in the copending patent application of John A. Spencer, Serial No. 637,854, filed Qctober 14, 1932, now Patent No. 1,972,832, patented September-.4, 1934, the temperature at which the thermostatic actuator or disc of the type herein employedsnaps may be varied or adjusted by placing a variable resilient load on the central movable portion of the disc. Adjusting means in accord with this principle are embodied in the present invention. They comprise, first, a member H of generally cylindrical shape, which projects through a central hole 99 in the disc 5!. Extending from the member H is a flange 19 having a downwardly directed edge 19 which bears against the upper surface of the disc 5! near the edge of the central opening 99. The member ll extends loosely through a suitable opening 11 in the circular portion 93 of member 29, and has an end portion 19 of reduced diameter forming a shoulder 8|. Seated on the shoulder 8i and freely rotatable with respect to the portion 19- is a circular plate 93, which is provided with a peripheral flange 95.

In the bracket H which extends from the frame 9 there is provided a slot 91 which receives a threaded member 89. The lower end of the member 89 is formed as a threaded spindle 9! of greater diameter, the threads of the spindle 9! being provided at a considerable angle. A spacer collar 93, on which is rotatably mounted a disc or dial 95 having a depending flange or apron 9?, is mounted on the member 99. The disc 99 and apron 97 project forwardly through a suitable opening 99 in the casing l5. On the apron 97 there is mounted a scale Nil, which includes indicia for the range of temperature variation over which it is possible to adjust the device. A cooperating arrow I93 (Fig. 1) permits adjustments to be securely effected from the front of the encased switch. The edge of the disc 99 is knurled as indicated at numeral E95 (Fig. 2) in order to permit of its ready manual rotation.

A nut i0? (Fig. 3) secures member 89 in position on the bracket ii, a washer 99 providing a surface against which the spacer collar 99 abuts. The nut 19? is so tightened that the member 99, with its spindle 9!, are non-rotatable with respect to the bracket ll, but the space provided by the collar 93 permits rotation of the disc 99. In order that the disc 99 may hold its manually adjusted position until it is desired to manually adjust it to some other position corresponding to a different temperature, a spring washer 99 is provided which resists by its friction unintentional motion of the disc 95. 1

Threadedly engaging the.spindle 9! is a nut I99, which is provided with a peripheral flange ill. The flange H i and the flange on member 93 are of the same diameter, and support therebetween a compression coil spring H9. The nut 199 also includes a radial slot H9, which receives a pin li'i mounted in the disc 99. This arrangement provides for coextensive rotation of the disc and the nut I99, the spindle 98, however, remaining stationary. As the nut I99 rotates, it'advances up and down the spindle 9i, and thus expands or compresses the spring H9. As the spring H9 rests at its lower end on member 89, its pressure is transmitted directly to the upper surface of thermostatic actuator disc 50. By this means a variable resilient pressure may be placed upon the disc 9! by manual rotation of the disc 95 from the exterior of the switch. The indicia on the strip iii! are suitably spaced in position to indicate directly the temperature of the medium in the pipe I at which the disc 9! will snap, as determined by the amount of resilient pressure exerted by the spring H9 thereon.

Extending upwardly from the disc 99 is a pin H9, which, by engaging with the blind ends of suitable depressions l2! (see Fig. 4) .in the brackis l - the central opening 69 in the disc et I1, positively limits rotation of the disc 95 in both directions.

The lead of the threads on spindle 9| is preferably made so great that the nut I09 will move substantially the entire length of said spindle 9| within the limits of rotation of the disc 95. Thus, a relatively wide variation of snapping temperatures may be achieved without an excessive amount of manual actuation.

The electrical switch means operated by the thermostatic actuator 5| will next be considered. Numeral I23 (Fig. 3) indicates a block of insulating material which is mounted by screws I24 on the bracket I9 extending from the frame 9. On its upper surface, the block I23 carries the stationary contact members of the switch, comprising two circular segments |25 (Fig. 6) and two terminal pieces I21. Between each of the pieces I25 and I21 there is provided a gap I29, the four pieces thus providing three gaps. The terminal pieces I21 are attached to connecting screws or binding posts |3| (Fig. 3) to which the ends of the cord or conduit 1 are attached. In order to make connections from one terminal I21 to the other terminal I21, the three gaps I29 must be bridged.

A central hole I33 in the block I23 slidably receives a pin I35. The pin I35 is threaded at its upper end I31, and thereon is screwed a ball member I39. The ball member I39 is received in a suitable recess MI in the lower end of the cylindrical member 1| which is positioned within The lower ends of the member 1| are turned inwardly as indicated at numeral I43 in order to retain the ball I39. There is thus provided a ball-andsocket or universal joint between the member 1| and the pin I35. Lock nuts I45 secure the ball member I39 tightly in position on the threaded pin I31.

Also threaded on the pin I35 is a collar I41. Resting relatively loosely upon the collar I41 is a circular plate I49 preferably made of insulating material. The plate I49 is held down against the collar I41 by a compression spring I5! surrounding the pin I35, the other end of the spring IISI reacting against a nut I53 also threaded on the pin I35.

The plate I49 carries three contact buttons I55 (see also Fig. 6) thereon. The buttons I55 are formed of electrical conducting material, and desirably have one of the structures shown in John A. Spencer Patents No. 1,697,886, No. 1,718,716, and No. 1,939,286. They are positioned each to bridge one of the gaps I29 between the stationary contacts I25 and I21.

When the disc 5| is in its upwardly dished position as indicated in Fig. 3, the plate I49 is lifted high enough so that the buttons I55 are removed from contact bridging position and thus the switch is opened. However, when the disc 51 over-centers to its downwardly dished position, its motion is transmitted to the pin I35 so that the plate I49 is dropped through a suflicient distance to bridge the gaps I29 with the contact buttons I55, thus closing the switch and hence the circuit. The buttons I55 are held firmly against the stationary contacts I25 and 121 by the compression of the spring :I5I, the adjustment being such that when contact is effected the plate I49 is slightly lifted oh the collar I41. When, now, the disc 5| again snaps to upwardly dished position, in the initial or creepage stage of its motion, no actual motion is imparted to the buttons I55, as the play provided by the collar I41 approaching the plate I49 is sufiicient to take care of this creepage motion. However, when the creepage is over and the disc 5| is in the actual snap portion of its travel, the collar I41 engages the plate I49 to lift the contact buttons I 55 and thus to break the circuit with a desired snap action.

In transmitting the snapping movement of the disc 53 to the pin I35, the ball-and-socket joint between the members 1| and I39 is very advantageous, as it compensates for any motion of the disc, or of the member 1|, that is not precisely in a true vertical direction. It has been discovered that a device which is constrained to move only vertically, as would be the case were the member 1| and the pin I35 to be permanently and rigidly secured together, exerts an inhibiting eiTect upon the snapping movement of the disc 5| if the parts happen to be slightly misaligned. The ball-and-socket joint, on the contrary, provides for a free movement of the disc 5|, without unwanted restrictions even if the parts are somewhat'misaligned. Rotation of the plate or disc I49 on the pin I35 is prevented by means of an upstanding pin I51 mounted in the lock I23, which is engaged by a radial slot I59 in said plate I49.

From the above it will be seen that a highly efficient and accurate thermostatically operated electric switch has been provided, and that this switch is accurately adjustable through a considerable range of temperature variations. The compact size and structure of the device as a whole makes it possible for it to be housed in a casing considerably smaller than the casings required for prior analogous devices.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in carrying out the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A thermostatic switch comprising a snapacting thermostatic disc, means supporting and enclosing said disc comprising a pair of members loosely clamping the periphery of said disc therebetween, said members having extensions in planes at angles thereto, said extensions being shaped to juxtapose the surface the temperature of which it is desired to control, said members and extensions being good conductors of heat whereby said disc is heated by conduction from the said surface, stationary contact means, and movable contact means cooperating therewith, said movable contact means being operatively connected to the movable part of said disc.

2. A switch as set forthin claim 1, in which the thermostatic disc is radially corrugated.

3. A switch as set forth in claim 1, including means placing a variable resilient pressure upon the movable part of said disc, whereby to vary the temperature at which the disc snaps.

4. A switch as set forth in claim 1, including means bearing upon the movable part of said disc, a compression spring bearing upon said lastnamed means, and means for varying the load upon said compression spring, whereby to vary the temperature at which the disc snaps.

5. In a thermostatic control, a thermostatic actuating element comprising a radially cor- 'rugated, snap-acting thermostatic disc, means.

mounting said disc at the periphery thereof, and means for placing a variable resilient load on the central movable portion of said disc, said last-named means comprising an element bearing upon the central portion of said disc, a relatively stationary'screw, anut rotatable on said screw, and a compression spring between said nut and said element, and means for rotating said nut to move it up and down said screw to vary the extent of compression of said spring.

6. In a thermostatic control, a thermostatic actuating element comprising a radially corrugated, snap-acting thermostatic disc, means mounting said disc at the periphery thereof, and means for placing a variable resilient load on the central movable portion of said disc, said last-named means comprising an element bearing upon the central portion of said disc, a screw, a nut rotatable on said screw, and a compression spring between said nut and said element, and means for moving said nut up and down said screw to vary the extent of compression of said spring.

7. In a thermostatic electric switch, a thermostatic elementicomprising a radially corrugated, snap-acting thermostatic disc having a. central opening therein, means mounting said disc at its periphery but leaving the central portion thereof free for movement in response to temperature change, means having a socket therein and passing through said central opening and movable with said disc, stationary contact means, movable contact means cooperating therewith, and means connected to said movable contact means and having a ball thereon, said ball being received by saidsocket, whereby a universal joint is provided between said disc and said movable contact means.

WILLIAM JAMES MCGOLDRICK. 

